Field of the invention
The present invention relates to an image sensor, a control method therefor, and an image capturing apparatus, and more specifically to an art of circuit configuring an image sensor.
Description of the Related Art
In recent years, in image capturing apparatuses using image sensors such as CMOS sensors, multifunctionality has progressed, and not only generation of captured images such as still images/moving images, but also control of image capturing apparatuses such as focus adjustment, for example, are performed based on information obtained from the image sensors.
For example, Japanese Patent Laid-Open No. 2001-124984 discloses a technique capable of performing focus detection using a pupil division method by using signals obtained from an image sensor. In Japanese Patent Laid-Open No. 2001-124984, by providing one microlens (ML) and two photodiodes (PD) for each pixel of the image sensor, respective PDs capture light passing through different pupil regions of the imaging lens. By comparing output signals from the two PDs of each pixel, focus detection becomes possible, and it is also possible to generate a captured image by adding the output signals from the two PDs for each pixel.
In addition, Japanese Patent Laid-Open No. 2016-21052 discloses a technique of acquiring signals for focus detection only from a part of rows in a screen.
However, in the conventional technique disclosed in the above-mentioned Japanese Patent Laid-Open No. 2001-124984, since it is necessary to read a focus detection signal in addition to an image signal, the readout time increases.
Further, in the technique disclosed in Japanese Patent Laid-Open No. 2016-21052, an increase in the readout time is suppressed by reading the focus detection signal only from a part of the rows in the screen. However, the readout time differs between in a row from which only the image signal is read out and in a row from which both the image signal and focus detection signals are read out. Consider, for example, a case where a subject moving at a high speed is captured by the rolling shutter driving method disclosed in Japanese Patent Laid-Open No. 2016-21052. In this case, in addition to the conventionally known rolling distortion phenomenon, distortion also occurs between the rows from which only the image signal is read out and the rows from which the image pickup signal and the focus detection signals are read out, and there is concern about giving the user a feeling of discomfort.